Bottom Line:
Application of JA to WT plants before thrips attack decreased the thrips population.Thrips feeding induced expression of these marker genes and significantly increased the JA content in B. rapa.Application of JA to B. rapa enhanced plant resistance to thrips, restricted oviposition, and reduced the population density of the following generation.

Background: The western flower thrips (Frankliniella occidentalis [Pergande]) is one of the most important insect herbivores of cultivated plants. However, no pesticide provides complete control of this species, and insecticide resistance has emerged around the world. We previously reported the important role of jasmonate (JA) in the plant's immediate response to thrips feeding by using an Arabidopsis leaf disc system. In this study, as the first step toward practical use of JA in thrips control, we analyzed the effect of JA-regulated Arabidopsis defense at the whole plant level on thrips behavior and life cycle at the population level over an extended period. We also studied the effectiveness of JA-regulated plant defense on thrips damage in Chinese cabbage (Brassica rapa subsp. pekinensis).

Results: Thrips oviposited more on Arabidopsis JA-insensitive coi1-1 mutants than on WT plants, and the population density of the following thrips generation increased on coi1-1 mutants. Moreover, thrips preferred coi1-1 mutants more than WT plants. Application of JA to WT plants before thrips attack decreased the thrips population. To analyze these important functions of JA in a brassica crop plant, we analyzed the expression of marker genes for JA response in B. rapa. Thrips feeding induced expression of these marker genes and significantly increased the JA content in B. rapa. Application of JA to B. rapa enhanced plant resistance to thrips, restricted oviposition, and reduced the population density of the following generation.

Conclusion: Our results indicate that the JA-regulated plant defense restricts thrips performance and preference, and plays an important role in the resistance of Arabidopsis and B. rapa to thrips damage.

Mentions:
Because the JA-regulated defense affected oviposition, we analyzed its effect on the subsequent generation. We put 20 adult females on WT and coi1-1 plants and counted adults, larvae, and pupae after 2 weeks. We covered the soil with fine zirconia beads 0.4 mm in diameter to find thrips easily. Thrips fed much more on coi1-1 mutants than on WT plants (Fig. 3A, B). About 14 of the original adult females remained on coi1-1 mutants, but only about 2 remained on WT plants (Fig. 3C). Similarly, while more than 190 larvae lived on the coi1-1 mutants, only about 20 lived on the WT plants (Fig. 3D). We also found 5 times as many pupae on coi1-1 mutants than on WT plants (Fig. 3E). These results demonstrate that the JA-regulated defense can determine thrips population size.

Mentions:
Because the JA-regulated defense affected oviposition, we analyzed its effect on the subsequent generation. We put 20 adult females on WT and coi1-1 plants and counted adults, larvae, and pupae after 2 weeks. We covered the soil with fine zirconia beads 0.4 mm in diameter to find thrips easily. Thrips fed much more on coi1-1 mutants than on WT plants (Fig. 3A, B). About 14 of the original adult females remained on coi1-1 mutants, but only about 2 remained on WT plants (Fig. 3C). Similarly, while more than 190 larvae lived on the coi1-1 mutants, only about 20 lived on the WT plants (Fig. 3D). We also found 5 times as many pupae on coi1-1 mutants than on WT plants (Fig. 3E). These results demonstrate that the JA-regulated defense can determine thrips population size.

Bottom Line:
Application of JA to WT plants before thrips attack decreased the thrips population.Thrips feeding induced expression of these marker genes and significantly increased the JA content in B. rapa.Application of JA to B. rapa enhanced plant resistance to thrips, restricted oviposition, and reduced the population density of the following generation.

Background: The western flower thrips (Frankliniella occidentalis [Pergande]) is one of the most important insect herbivores of cultivated plants. However, no pesticide provides complete control of this species, and insecticide resistance has emerged around the world. We previously reported the important role of jasmonate (JA) in the plant's immediate response to thrips feeding by using an Arabidopsis leaf disc system. In this study, as the first step toward practical use of JA in thrips control, we analyzed the effect of JA-regulated Arabidopsis defense at the whole plant level on thrips behavior and life cycle at the population level over an extended period. We also studied the effectiveness of JA-regulated plant defense on thrips damage in Chinese cabbage (Brassica rapa subsp. pekinensis).

Results: Thrips oviposited more on Arabidopsis JA-insensitive coi1-1 mutants than on WT plants, and the population density of the following thrips generation increased on coi1-1 mutants. Moreover, thrips preferred coi1-1 mutants more than WT plants. Application of JA to WT plants before thrips attack decreased the thrips population. To analyze these important functions of JA in a brassica crop plant, we analyzed the expression of marker genes for JA response in B. rapa. Thrips feeding induced expression of these marker genes and significantly increased the JA content in B. rapa. Application of JA to B. rapa enhanced plant resistance to thrips, restricted oviposition, and reduced the population density of the following generation.

Conclusion: Our results indicate that the JA-regulated plant defense restricts thrips performance and preference, and plays an important role in the resistance of Arabidopsis and B. rapa to thrips damage.